Handheld computing and communication devices are well known. Cellular telephones, personal digital assistants (PDAs), and small form factor computers all require input from a user in order to operate. Typically, these handheld device have a processor connected to a memory, a screen and a user input device. The screen typically provides either a text or graphical interface through which options or applications are selected. In many instances a selection is made by use of a directional input device, such as a touchpad, rollerball, directional keypad, or thumbwheel. These options allow the user to position a pointer or a cursor on the list application or option desired. These directional input devices allow a user to select options, launch applications, and move pointers or cursors. Typically the directional input device works in conjunction with some variety of action button, such as a mouse button, or an integrated selector as used in many thumbwheel devices.
Directional input devices produce signals which are further processed by the handheld device to represent a direction to an element of the handheld device user interface. For example, in operations involving the displacement of a cursor on a screen, a handheld device user presses, rolls, touches, or exerts pressure on some directional sensor. The pattern of the physical parameter is converted into signals processed by the handheld, and ultimately the cursor or a pointer moves.
Directional input devices can be classified as having either one, or a plurality of degrees of freedom. Devices that have one degree of freedom are restricted to providing directional input in one dimension, for instance up-down, or left-right, but not both. In input devices with a plurality of degrees of freedom, several directions are possible, for instance both up-down and left-right. In typical directional input devices, only two dimensions are tracked. Though there are devices for tracking three dimensional input, typically these devices are used in conjunction with very specialised user interfaces. The quality of directional signals depends on the attributes of the sensed pattern of physical parameters, which ultimately depend on the type of sensors. For instance, simple push-buttons or keys can only detect directional presence-either the key is pressed, or it is not. On the other hand, a roller or touch surface can detect directional degree.
The layout of the handheld device is determined by a number of ergonomic and aesthetic constraints. One of the greatest constraints is the overall size of the device, which for reasons of portability is tightly constrained. As a result of their small form factors, handheld devices typically trade off a desirable large screen, for necessary input device space. Without enlarging the handheld device, a larger screen must come at the cost of a smaller input device. There exist a number of well-known, convenient directional input devices, such as computer mice, trackballs and touchpads, that address a number of concerns in directional input devices. However, these devices either require a great deal of space or cannot be easily integrated with a portable handheld device.
To accomplish the reduction in input device size, many people have attempted to eliminate a distinct directional input device. Some devices have eliminated the distinct directional input device by employing a touch sensitive screen. This allows the user to select an option or application directly on the screen. This however, typically requires at least a rudimentary directional input device to allow scrolling through pages. Additionally, it requires two-handed operation, which is not always possible, and should not be necessary to perform simple tasks with the handheld device.
Another strategy is to employ a thumbwheel, such as a jog-dial, which can be place on the side of the handheld. This removes the directional input device from the face of the device and can save considerable space. By combining the simplicity of a roller, with optimal placement for use with the thumb, a thumbwheel is provided on handheld devices for directional input. A thumb roll in a first direction is interpreted as a directional input corresponding to a positive displacement on a first primary direction, such as up, whereas a thumb roll in a second opposite displacement is interpreted as a directional input corresponding to a negative displacement along the same first direction. Furthermore, by detecting a presence condition, such as the user holding down an “alt” key, at the same time as a thumb roll, the thumb roll can be interpreted to provide a pointer or cursor displacement in a second direction. Thus a thumbwheel can be adapted to provide multidirectional input. An example of bi-directional input, a specific type of multidirectional input, is the displacement of a cursor in a text editor pane wherein one direction corresponds to the character position of the cursor and wherein the other direction corresponds to the line number of the cursor. Though thumbwheels address many concerns, the thumbwheel requires a rotatable key to be installed in the handheld, which is only on one side of the device. The positioning of the directional input device on the side of the device makes the device difficult to use for either right or left handed people. Additionally, because the handheld is of a standard size, the positioning of the thumbwheel can make the device difficult to use for people with large or small hands. Furthermore, the thumbwheel, as with any mechanical device, is subject to mechanical wear and failure, and additionally increases the cost of manufacturing the mould for the device's exterior due to the additional apertures required.
In classifying directional input devices it should be noted that directional input devices can have both presence and degree. The simplest directional input device has presence, such as for example in an arrangement of pressure sensors such as buttons, each of which is associated with a fixed increment in a particular direction, such as is the case for example with arrow keys. Either a key is pressed, or it is not. The user's input has presence in one particular direction and is sensed in this fashion and the handheld device is signalled accordingly.
More advanced directional input devices can provide directional degree. Directional degree is related to the magnitude of displacement along a physical degree of freedom of the sensor. For instance, in a roller sensor, the degree of roller activity is proportional to the displacement of the roller and has the same sign as the direction of displacement. The degree of user activity in a direction is sensed in this fashion and the handheld device is signalled accordingly. Degree can be simulated in devices that can only provide presence through mechanisms such as key repeat rate, which provides a plurality of presence signals if the input device is activated for a sufficient amount of time. Some directional input devices have both presence and degree, such as a rollers or touch surfaces, that are combined with at least one button.
Directional input devices can also be categorized by the degrees of freedom that they provide. Directional input devices which have only one physical degree of freedom, such as thumbwheels, are typically used to provide directional input restricted to a single path. Directional input devices which have more than one degree of freedom are traditionally used in multidirectional input, such as for example a capacitive touch surface type sensor manipulated with the finger or a stylus. Directional input devices with several degrees of physical freedom tend to be more expensive and complex to operate than sensors with only one degree of freedom.
As described above, sensors with only one physical degree of freedom, a presence based control can be used to select alternate directions, which are typically perpendicular to the primary direction, thereby providing simulated multidirectional input. An example is the aforementioned a thumbwheel which moves a cursor in one dimension in a native state, but moves the cursor in a perpendicular direction when an “alt” key is depressed.
In the case of sensors with several degrees of freedom, presence can be used to constrain the directional input signals to a major direction, such as horizontal, vertical, or diagonal, thereby providing a simulated unidirectional input, which facilitates the drawing of a straight line on a freeform surface such as a touchpad. To achieve this, a user could use a touch surface to draw a diagonal line, and then hold an action key to constrain the line to the direction of the largest component, either horizontal or vertical.
Current techniques of directional input control of handhelds often combine varied sensor types and methods to provide varied forms of directional input, each of which presents some advantages but unfortunately also has drawbacks.
Added user operational complexity may be required for simulated uni-dimensional input on devices using traditional multidegree of freedom directional input devices. The same can be said for simulated multidimensional input using traditional single degree of freedom directional input devices. The mere combination of the two types of input devices, such as providing both a thumbwheel and a touch surface, overcomes many problems, but still requires the expensive tooling required to install a thumbwheel, and does not eliminate the valuable area required by the touchpad.
There is therefore a need for a directional input device with a minimized size, to allow for a larger screen, while reducing the tooling costs associated with apertures on the moulding of the handheld device. There is a further need for a directional device that is capable providing directional input to a handheld without requiring dual handed operation, and without providing a preference to right handed people, left handed people, or people with a particular size of hand.